Chapter 12. 



DISEASES OF LEAVES (contd.}. 



Rusts. The Wheat Rust. Life Story of the fungus, relation to 

 the Barberry. The Mint Rust and Hollyhock Rust as examples 

 of other Rust diseases. 



The Rusts constitute a very important group of plant 

 diseases, which includes some of the most widely dis- 

 tributed and highly destructive of parasitic fungi. The 

 grain-producing plants and grasses of our fields, the 

 plants of our gardens and greenhouses, and even forest 

 and fruit trees are attacked by members of the rust 

 family of fungi. Of all plant diseases they are in many 

 respects the most remarkable, as they are also the most 

 difficult to combat. Whilst the nature and the life history 

 of the fungi causing them have only been known for a 

 relatively short period, the blighting effects caused by out- 

 breaks of these maladies are referred to by writers of the 

 remotest antiquity. Throughout the centuries wheat rusts 

 have been responsible for great damage wherever wheat 

 has been grown, and at the present time the loss caused 

 to the wheat crop alone throughout the world amounts" to 

 many millions of pounds annually. 



